U.S. Pat. No. 6,012,826 discloses an illuminating balloon, which includes a bulb-protecting unit 14 integrated in an inflatable envelope 12. The bulb-protecting unit 14 is a fixedly sized grid downward closed to cover a bulb 16 therein. The bulb-protecting unit 14 is provided at a top with a rivet 46, which upward extends through a top of the envelope 12 to engage with a rivet thimble 48, so as to connect the upper end of the bulb-protecting unit 14 to the top of the envelope 12.
The following disadvantages are found in the above-structured illuminating balloon:    1. The rivet 46 upward extended through the top of the envelope 12 to engage with the rivet thimble 48 would inevitably produce a hole on the envelope 12, and rainwater would permeate into the envelope 12 via the hole to cause short circuit of the bulb 16 inside the envelope 12.    2. The fixedly sized bulb-protecting unit 14 is not height-adjustable, and is only adaptable to envelopes of the same size corresponding to that of the bulb-protecting unit 14. For other envelopes 12 of different sizes, separate bulb-protecting units 14 must be produced.    3. The fixedly sized bulb-protecting unit 14 could not be disassembled and stacked, and would therefore occupy a relatively large space and could not be conveniently carried, transported, and stored.    4. Once the bulb-protecting unit 14 is fixed to the top of the envelope 12 via the rivet 46, it is not rotatable relative to the envelope 12. Under this condition, the envelope 12 tends to tangle with the bulb-protecting unit 14 in the process of inflating.    5. The bulb-protecting unit 14 includes an integrally formed grid that would block part of the light from the bulb 16 to produce considerably significant shadows on the envelope 12 to adversely affect the appearance of the illuminating balloon.    6. A blower seat 18 is located at a bottom end of the envelope 12 for mounting a blower 52 thereto. Since the blower seat 18 does not include any air-relieving hole, the envelope 12 tends to flutter when it is too quickly inflated using the blower 52.